The invention concerns a positioning device.
Identification devices are known having a scanning device and supports with a so-called barcode consisting of a number of parallel, contrasting lines of various thicknesses and/or placed at various distances from one another. These code lines are all at right angles to the normal scanning direction of the scanning device.
Such identification devices are quite sufficient when the only purpose is to obtain information regarding the price, the nature or manufacturing data of a product or object the code line or lines are related to.
However, when it comes to determining a position, in other words when the support with the code line or lines and the scanning device must be positioned in relation to one another, the above-mentioned known barcode with code lines directed at right angles to the scanning direction will not suffice.
This is for example the case when guiding automatically controlled vehicles in warehouses or workshops and such in. The vehicles are guided, for example, over guides mounted in the floor and have to leave their normal course at certain positions and have to stop at a certain position to be identified. This is, for example, also the case with automatically controlled lifts, among others in automatic warehouses, which have to pick up an object from or place it in a certain position to be identified in a stacking rack.
Until now, for exact positioning, use is made in such cases of a double system per positioning device.
The target position is closely approached at high speed by means of a conventional positioning system on the one hand, after which the target position is exactly detected at low speed by means of another system.
Especially in systems with large variations in load and/or systems whereby under the influence of variable loads or other external influences relative shifts in place or mechanical distortions occur, this working method is relatively slow. In many cases, a system will have to wait for the positioning in one direction until another system has completed the positioning in another, usually perpendicular direction, which also reduces the speed.
Moreover, if every position has to be unambiguously identified, an extra identification system will have to be added.